I tried to make a solar oven a few years ago and it was an epic fail!
It was a middle school science project for my daughter.
The person in the tutorial used styrofoam display boards covered with heavy foil and cut into four tulip petal shapes which were lashed together with shoelaces.
It was about 80 degrees outside. We set the thing up as recommended.
Several hours later we had a mini bundt pan with warm chocolate goo and some kind of yellow goo that was supposed to be an egg.
There was also-from a different tutorial-a shoebox lined with black paper and it had a glass cover from a picture frame. That was a dud too.
If I had a better tutorial or a real solar oven maaaaybe it might work. though.
There was a lady from Florida University Extension gave a good video using Styrofoam container - just a box no tulips. LOL